Free-piston engine cup piston valve design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Free-piston engines face issues with internal resistance and reduced engine life due to the mixing of ignitable mixtures with burnt gases, leading to sooting and sealing problems between the piston rod and housing.
Innovation Solution
The piston rod is coupled with a cup piston that forms a valve, allowing fuel injection via the piston rod ends, preventing mixture mixing with combusted gases, and using air jackets for low-friction movement, with differential pressure actuating the valve and labyrinth grooves supporting sliding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the piston rod is positioned inside the combustion chamber to perform work, then the engine can generate power, but the ignitable mixture mixes with burnt gases causing sooting and reduced engine lifespan
Solution Approach 1:
The piston rod is extracted from the combustion chamber and positioned in the compressor chamber instead. The cup piston extends into the combustion chamber to perform the sealing and valve functions, while the piston rod remains outside the combustion chamber in the compressor chamber, preventing mixture-burnt gas contamination.
Solution Approach 2:
The cup piston serves as an intermediary component that performs multiple functions: it seals the combustion chamber, acts as a valve by opening/closing transfer ports, and transmits force from the piston rod outside the combustion chamber to the combustion process inside, without allowing direct contact between the piston rod and combustible mixture.
2Power
If the piston rod moves within the combustion chamber, then work can be performed during combustion, but carbon buildup occurs on the piston rod reducing engine life
Solution Approach 1:
The piston rod is extracted from the combustion chamber environment and relocated to the compressor chamber. This physical separation eliminates the piston rod's exposure to combustible mixture and burnt gases, preventing carbon deposition on the piston rod surface while the cup piston handles combustion chamber sealing.
3Reliability
If a seal is used between the piston rod and housing to prevent leakage, then sealing is achieved, but internal resistance increases and engine performance decreases
Solution Approach 1:
Air pressure is utilized to create sealing between the cup piston and the combustion chamber wall, as well as between the piston rod and compressor chamber. The pressure differential during operation maintains the seal without requiring mechanical contact, eliminating friction and internal resistance associated with traditional seals.
Solution Approach 2:
The sealing mechanism transitions from mechanical contact-based sealing to pressure-based sealing. By changing the sealing parameter from physical contact to pressure differential, the system achieves effective sealing while minimizing friction and energy loss.
4Ease of operation
If the piston rod is extended into the combustion chamber to control valve timing, then precise valve actuation is achieved, but the valve mechanism becomes complex with multiple moving parts
Solution Approach 1:
The cup piston combines multiple functions into a single component: it seals the combustion chamber, acts as a valve by opening/closing transfer ports through its movement, and transmits force from the piston rod. This merging eliminates the need for separate valve mechanisms while maintaining precise timing control through the cup piston's position during its stroke.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design minimizes internal resistance, prevents sooting, and enhances engine efficiency by ensuring the combustible mixture does not mix with burnt gases, resulting in improved engine life and performance.
Implementation Method 1
the cup pistons slide on air without requiring lubricant; specifically, an air jacket forms between their outer surfaces and the cylinder liners, and another between their inner surfaces and the cylinders
Implementation Method 2
at least one bore is located at each piston rod end, which forms an injection nozzle, through which fuel, which mixes with air supplied in the area of the valve, enters the respective combustion chamber
Implementation Method 3
the valve, which is formed between each cup piston and the respective piston rod end, is actuated by the differential pressure that arises between the compressor chamber and the combustion chamber during the operation of the free-piston engine
Data Source
Figure 1
Figure 1a
Figure 1b~1c
AI summary
Free-piston engine in a cylindrical-elongated, two-sided symmetrical design with a stationary base part (1) and two identically designed engine halves, each with a combustion chamber (C) and with a oscillating body (6) sliding within the base part (1) having a piston rod (8) and compressor chambers (B) between the piston rod (8) and the base part (1).The piston rod (8) is coupled at its ends to a cup piston (19) at each end, which encloses one of the combustion chambers (C) and together with the respective piston rod end forms a valve (9), wherein each cup piston (19) is mounted in a barrel sleeve (3) belonging to the base part (1) and on a cylinder (22) of a cylinder plate (5) belonging to the base part (1) which encloses the combustion chamber (C), which together with the barrel sleeve (3) encloses a damper chamber (D) into which air is drawn during operation of the engine, wherein at each piston rod end of the piston rod (8) there is at least one bore (8a) which forms an injector nozzle (8b) through which fuel, which mixes with air supplied in the area of the valve (9), enters the respective combustion chamber (C) in the region of bottom dead center and when the valve (9) is open.